1. Field of the Invention
This invention relates to apparatus for the generation of radio-frequency power at microwave frequencies and more specifically to apparatus for combining the power generated by a plurality of individual semiconductor devices without producing undesirable modes of oscillation or destructive interaction between the semiconductor devices that are generating the power.
2. Description of the Prior Art
In the past, the generation of power by semiconductor devices operating in the negative resistance region has been severely limited in the amount of power that has been obtainable. As a result, various efforts have been undertaken to permit the combination of the power generated by the individual semiconductor oscillators. However, the combining networks of the past have been complex and, further, often produced oscillations at various undesired frequencies and with varying degrees of instability. This was particularly true in devices operating at the microwave frequencies because the physical sizes of the units involved easily become important multiples of a quarter wavelength at the operating frequencies, thus producing, or tending to produce, multiple resonances of the circuits including the semiconductor devices.
Further, oscillators including multiple diodes, particularly when they are pulsed to levels of 10 to 20 watts with 20% to 30% duty cycles, may generate such quantities of heat that destruction of the diode junctions is a distinct possibility. At the same time, resorting to such devices as klystrons, traveling wave tubes, backward-wave oscillators and magnetrons is not an acceptable course of action, particularly in those applications where compactness and minimal weight are paramount. Thus, solving the problems of spurious moding, limited power and destructive heat-rise in the semiconductor devices utilized in such microwave oscillators is the only acceptable course of action.
Accordingly, it is a general object of this invention to provide a semiconductor microwave oscillator which is free of the problems set forth hereinbefore.
It is a further object of this invention to provide a microwave oscillator which permits paralleling the semiconductor devices utilized in the oscillator without experiencing undesirable spurious frequency generation or semiconductor device deterioration.
It is a still further object of this invention to provide a microwave oscillator which utilizes multiple avalanche diodes operating in the IMPATT mode and coupled in parallel for increased output without suffering from spurious oscillations.